Extraction of aromatic with a salt modified solvent

ABSTRACT

A PROCESS FOR SEPARATING A NON-AROMATIC HYDROCARBON FRACTION AND AN AROMATIC HYDROCARBON FRACTION FROM A MIXTURE THEREOF WHEREIN THE MIXTURE IS CONTACTED AT A TEMPERATURE BETWEEN ABOUT 200*F AND ABOUT 400*F WITH AN EXTRACTION SOLVE OF A HIGHLY POPLAR ORGANIC LIQUID HAVING 10-50 WEIGHT PRECENT OF SOLUBLE METAL SALT DISSOLVED THEREIN. PREFERABLY A SALT OF LITHIUM, BERYLLIUM OR MAGNESIUM, WHEREBY THE AROMATIC HYDROCARBON FRACTION IS EXTRACTED FROM THE MIXTURE. THE EXTRACTION SOLVENT IS COOLED TO A TEMPERATURE BELOW ABOUT 150*F., AT WHICH TEMPERATURE A SUBSTANTIAL PORTION OF THE AROMATIC HYDROCARBON FRACTION IS INSOLUBLE THEREIN. ANY REMAINING AROMATIC HYDROCARBON FRACTION MAY BE RECOVERED FROM THE EXTRACTION SOLVENT BY CONTACTING THE EXTRACTION SOLVENT WITH A NON-AROMATIC HYDROCARBON SOLVENT AT A TEMPRATURE NO GREATER THAN 150*F., AT WHICH TEMPERATURE THE AROMATIC HYDROCARBON FRACTRION IS SELECTIVELY EXTRACTED FROM THE EXTRACTION SOLVENT.

Feb. 2, 1971 p GELBEIN ET AL 3,560,375

EXTRACTION 0F AROMATICS WITH A SALT MODIFIED SOLVENT Filed April 28. 1969 4 Sheets-Sheet 1 IN VENTORS Abraham P. Gelbein William Dimoplon, Jr.

makjmyamtii ATTORNEYS Feb. 2, 1971 p GELBE|N ET AL 3,560,375

EXTRACTION OF AROMATICS WITH A SALT MODIFIED SOLVENT Filed April 28, 1969 4 Sheets-Sheet 2 INVENTORS Abraham P. Gelbein By William Dimoplon, Jr.

AT TORNEYS A. P. GELBEIN ETA!- EXTRACTION OF AROMATICS WITH A SALT MODIFIED SOLVENT Filed April 28. 1969 Feb. 2, 1971 4 Sheets-Sheet 3 .m N S 5 e n Y R b 0 E m am N G O R m P m V 0 M W M m mm mm Em h (9 UK k i R E vow now B =5 1' new low mam M u 19 SN Feb. 2, 1971 EXTRACTION Filed April 28, 1969 A. P. GELBEIN ETAL OF AROMATICS WITH A SALT MODIFIED SOLVENT 4 Sheets-Sheet t Q m V INVENTORS Abraham P. Gelbein AT TORNEYS William Dimoplon, Jr.

United States Patent 3,560,375 EXTRACTION OF AROMATIC WITH A SALT MODIFIED SOLVENT Abraham P. Gelbein, Plainfield, and William Dimoplon,

Jr., Bloomfield, N.J., assignors to The Lummus Company, Bloomfield, N.J., a corporation of Delaware Filed Apr. 28, 1969, Ser. No. 819,743 Int. Cl. Cg 21/02; C07c 7/10 US. Cl. 208-324 14 Claims ABSTRACT OF THE DISCLOSURE A process for separating a non-aromatic hydrocarbon fraction and an aromatic hydrocarbon fraction from a mixture thereof wherein the mixture is contacted at a temperature between about 200 F. and about 400 F. with an extraction solvent of a highly polar organic liquid having 1050 weight percent of soluble metal salt dissolved therein, preferably a salt of lithium, beryllium or magnesium, whereby the aromatic hydrocarbon fraction is extracted from the mixture. The extraction solvent is cooled to a temperature below about 150 F., at which temperature a substantial portion of the aromatic hydrocarbon fraction is insoluble therein. Any remaining aromatic hydrocarbon fraction may be recovered from the extraction solvent by contacting the extraction solvent with a non-aromatic hydrocarbon solvent at a temperature no greater than 150 F., at which temperature the aromatic hydrocarbon fraction is selectively extracted from the extraction solvent.

This invention relates to the separation of liquid mixtures and more particularly to a process for separating an aromatic hydrocarbon fraction and a non-aromatic hydrocarbon fraction from mixtures thereof.

In many commercial processes, such as petroleum refining, there is need to separately recover various hydrocarbon fractions from mixtures thereof. Although such separations can be effected by fractional distillation, in many cases the boiling points or boiling ranges of the various hydrocarbon fractions are sufiiciently close to make separation by fractional distillation very difiicult. In such cases, a solvent extraction technique is required to effect the separation.

An object of this invention is to provide a new and improved process for separating aromatic hydrocarbon and non-aromatic hydrocarbon fractions from mixtures thereof.

Another object of this invention is to provide a process for separating aromatic hydrocarbon and non-aromatic hydrocarbon fractions from mixtures thereof by selectively extracting aromatic hydrocarbons from the mixture.

A further object of this invention is to provide a process for recovering essentially pure aromatic hydrocarbon and non-aromatic hydrocarbon fractions from mixtures thereof.

Yet another object of this invention is to provide a continuous process for recovering aromatic hydrocarbon and non-aromatic hydrocarbon fractions from mixtures thereof that may be economically operated on a commercial basis.

These and other objects of the invention should be more readily apparent from the following detailed description thereof when read with reference to the accompanying drawings wherein:

FIG. 1 is a simplified schematic flow diagram of an embodiment of the process of the invention;

FIG. 2 is a simplified schematic flow diagram of another embodiment of the process of the invention;

3,560,375 Patented Feb. 2, 1971 ice FIG. 3 is a simplified schematic fiow diagram of a further embodiment of the process of the invention; and FIG. 4 is a simplified schematic flow diagram of still another embodiment of the process of the invention.

The objects of the invention are broadly accom plished by selectively extracting at an elevated temperature an aromatic hydrocarbon fraction from a liquid hydrocarbon mixture, containing an aromatic hydrocarbon fraction and a non-aromatic hydrocarbon frac- 10 tion, with an extraction solvent selective for aromatics having a metal salt modifier dissolved therein, followed by cooling of the extraction solvent, containing the aromatic hydrocarbon fraction, to separate the aromatic hydrocarbon fraction therefrom.

The extraction solvent, as hereinabove noted, contains a highly polar organic liquid in that such liquids have a high selectivity for aromatic hydrocarbons. The highly polar organic liquids which are employed for selective extraction of aromatic hydrocarbons are gen erally known in the art and as representative examples of such liquids which may be employed singularly or in combination with each other, there may be mentioned: saturated lower hydrocarbon alcohols, such as the alkanols, preferably methanol, alkane diols; e.g., propylene glycol; phenols; lower acyclic and heterocyclic hydrocarbon alcohol ethers, such as tetrahydrofurfural alcohol, methyl cellosolve, diethylene and thiethylene glycol and the like; lower hydrocarbon (preferably acyclic) sulvones, such as tetramethylene sulfone and the like; lower acyclic and heterocyclic hydrocarbon amines and (preferably hydroxy) hydrocarbon nitrilies, such as proprionitrile, hydroxy proprionitrile and the like;

lower acyclic and heterochclic hydrocarbon amines and substituted (preferably hydroxy) hydrocarbon amines, such as ethylene diamine, ethanol amine, N-methyl ethanol amine, pyridine and the like; acyclic and heterocyclic hydrocarbon amides, preferably lactams and substituted amides, such as formamide, dimethyl formamide, pyrrolidone, N-methyl pyrrolidone and the like; lower hydrocarbon (preferably acyclic) sulfoxides, such as dimethyl sulfoxides and the like. The term lower as used herein denotes no more than about seven carbon atoms.

The extraction solvent, as hereinabove noted, contains metal salt modifier which is soluble in the highly polar organic liquid and stable under process conditions, the salt functioning to change the selectivity characteristics of the highly polar organic liquid whereby the aromatic hydrocarbon fraction is rendered less soluble in the extraction solvent by cooling of the extraction solvent containing dissolved aromatic hydrocarbon, thereby permitting recovery of the aromatic hydrocarbon fraction. As representative examples of such metal salts which may be employed either singularly or in combination with each other, there may be mentioned salts of the following metals: copper, silver, beryllium, magnesium, zinc, tin, vanadium, arsenic, antimony, bismuth, chromium, manganese, iron, cobalt, nickel, palladium and platinum, with the anion of the salt generally being either a halide, nitrate, perchlorate, thiocyanate, acetate, citrate, benzoate, or the like. The extraction solvent generally contains from about 10 to about weight percent, preferably from about 15 to about 30 weight percent, of the metal salt, based on the highly polar organic liquid. The preferred salt modifiers are salts of lithium, beryllium and magnesium, and the preferred extraction solvent is methanol having lithium chloride dissolved therein.

It is to be understood that the specifically mentioned highly polar organic liquids and metal salt modifiers have only been presented to illustrate the extraction solvents of the invention and the selection of the particular salt for use with the particular solvent is deemed to be within the scope of one skilled in the art.

The non-aromatic hydrocarbon fraction of the mixture treated in accordance with the invention includes either an alkane or alkene, cycloalkenes or cycloalkane, including mono and polycyclic cycloalkanes generally classified as naphthenes, or mixtures thereof and is preferably saturated, and the aromatic hydrocarbon fraction includes either unsubstituted or hydrocarbon substituted aromatics, including olefinically unsaturated hydrocarbons, and the aromatic portion may be either mononuclear; e.g., benzene, styrene, toluene, etc. or polynuclear; e.g., naphthalene, anthracene and hydrocarbon substituted derivatives thereof. The non-aromatic hydrocarbon fraction may contain one or more non-aromatic hydrocarbons and similarly the aromatic hydrocarbon fraction may contain one or more aromatic hydrocarbons.

The liquid hydrocarbon mixture, including an aromatic and a non-aromatic hydrocarbon fraction, is contacted with the extraction solvent hereinabove described in a suitable liquid-liquid contacting device at an elevated temperature and at a pressure sufiicient to maintain all components in the liquid phase. As a result of such contacting at the elevated temperature the aromatic hydrocarbon fraction is selectively extracted from the liquid hydrocarbon mixture and a non-aromatic hydrocarbon fraction, essentially free of aromatic hydrocarbons, is separated from the extraction solvent now containing the aromatic hydrocarbon fraction dissolved therein. In accordance with the invention, the aromatic hydrocarbon fraction may be recovered from the extraction solvent by cooling the extract to a temperature at least about 100 F. lower than the extraction temperature, since at such lower temperatures the aromatic hydrocarbon fraction is appreciably less soluble in the extraction solvent. An aromatic hydrocarbon fraction, essentially free of non-aromatic hydrocarbons, is readily separated from the extraction solvent; e.g., by decantation. The particular temperatures employed during the extraction and cooling stages will vary with the extraction solvent employed and feed treated, with the aromatic hydrocarbon fraction being more soluble with increases in temperature and less soluble with decreases in temperature and the choice of optimum conditions is deemed to be within the scope of one skilled in the art. In general, the extraction is effected at temperatures from about 200 F. to about 400 F. and the aromatic fraction is recovered by cooling to a temperature less than about 150 F., preferably from about 100 F., to about 120 F.

In a preferred embodiment of the invention, the extraction solvent still containing some aromatic hydrocarbon fraction, may be further treated to recover the aromatic hydrocarbon fraction therefrom. In accordance with the preferred embodiment, the extraction solvent, still containing some aromatic hydrocarbon fraction, is contacted with a liquid non-aromatic hydrocarbon extraction solvent in a suitable liquid-liquid contacting device at a temperature similar to the temperature at which the aromatic fraction was separated from the extraction from solvent (as hereinabove noted in accordance with preferred operating conditions the temperature is no greater than about 150 F., preferably between about 100 F. and about 120 F.) and a pressure sufficient to maintain all components in the liquid phase. As a result of such contacting at a lower temperature, the aromatic hydrocarbon fraction tends to dissolve in the non-aromatic hydrocarbon solvent, in contradistinction to the initial processing step at a high temperature wherein the aromatic hydrocarbon fraction dissolves in the extraction solvent, whereby the aromatic hydrocarbon fraction is extracted from the extraction solvent. The extraction solvent, now essentially free of any aromatic hydrocarbon fraction may be reemployed in the initial extraction for separating an aromatic and non-aromatic hydrocarbon fraction from a mixture thereof. Sut h removal of the aromatic hydrocarbon constituents from the extraction solvent makes possible a high degree of separation of the aromatic constituents from the raffinate. Thus, high recovery of the aromatic constituents of the feedstock mixture can be achieved.

The non-aromatic hydrocarbon solvent employed to extract the aromatic hydrocarbon fraction from the extraction solvent is comprised of components similar to those described with respect to the non-aromatic hydrocarbon fraction in the liquid hydrocarbon mixture which is the feed to the process. In addition the non-aromatic hydrocarbon solvent should have a boiling point or boiling range sufficiently higher or lower than the boiling point or range of the aromatic hydrocarbon fraction so that the aromatic hydrocarbon fraction may be recovered therefrom by fractional distillation. Thus, for example, in the extraction of a naphtha feedstock the non-aromatic hydrocarbon solvent may have a boiling point or range lower than the boiling range of the naphtha; e.g., a light paraffin, such as propane, butanes, pentanes or mixtures thereof, or may have a boiling point or range higher than the boiling range of the naphtha feedstock; e.g., kerosene, gas oils etc., which are preferably highly saturated.

In accordance with another embodiment of the invention, a non-aromatic hydrocarbon solvent is also employed in the initial extraction for separating the aromatic and non-aromatic hydrocarbon fraction, in conjunction with the extraction solvent, to reduce the quantity of extraction solvent required in the initial contacting. The non-aromatic hydrocarbon solvent should have a boiling point or range sufficiently higher or lower than the boiling point or range of all components in the liquid hydrocarbon mixture so that the non-aromatic hydrocarbon solvent may be recovered from both the non-aromatic hydrocarbon fraction and the aromatic hydrocarbon fraction by fractional distillation.

The invention will be further described with reference to the embodiments thereof illustrated in the drawings and it is to be understood that such embodiments merely illustrate the invention without limiting the scope thereof. It is also to be understood that certain equipments, such as, pumps, valves, etc., have been omitted from the drawings to facilitate the description thereof and the use of such equipments at appropriate places is deemed to be within the scope of those skilled in the art.

Referring now to FIG. 1, a feed containing aromatic and non-aromatic hydrocarbon fractions, such as, a 200- 300 F. ASTM boiling range naphtha, in line 10 is passed through heat exchangers 11 and 12 to effect heating thereof to a temperature suitable for extraction of the aromatic hydrocarbon fraction therefrom by indirect heat transfer with extract from an extraction column, as hereinafter more fully described, and a suitable heat transfer agent; e.g., steam, respectively. The heated mixture from heat exchanger 12 in the line 13 is introduced into the lower portion of an extraction column 14, containing a plurality of suitable liquid-liquid contacting devices, such as trays, and operated at a temperature within the range between about 200 F. and about 400 F. and a pressure sufiicient to maintain components in the liquid phase. A lean extraction solvent of the type hereinabove described, such as methanol containing 20 weight percent of lithium chloride, is introduced into the top of extractor 14 through line 15 and additional extraction solvent is introduced through line 16 at an intermediate portion of the extractor 14. The extractor 14 is provided with an aromatic hydrocarbon reflux through line 17 located at the bottom of the extractor 14. As a result of the contact between the mixture and the extraction solvent, the aromatic hydrocarbon fraction is extracted from the mixture with a non-aromatic hydrocarbon raflinate, essentially free of aromatic hydrocarbons, being withdrawn from the top of the extractor 14 through line 18 and an extract comprised of a solution of the aromatic hydrocarbon fraction in the extraction solvent, essentially free of non-aromatic hydrocarbons, is withdrawn from the bottom of the extractor 14 through line 19.

The extract in line 19 is passed through heat exchangers 11, 21, 22 and 23 to effect cooling thereof to a tempera ture below 150 F., preferably to a temperature within the range between about 100 F., and about 120 F. by indirect heat transfer with extraction solvent being recycled to the extractor 14 through line 15, extraction solvent being recycled to the extractor 14 through line 16, feed in line and a suitable coolant, such as water, respectively. As a result of such cooling, a major portion of the aromatic hydrocarbon fraction is now insoluble in the extraction solvent and a two-phase mixture is passed from heat exchanger 23 through line 24 into a settling drum 25 to separate the two phases.

An aromatic hydrocarbon phase, containing some extraction solvent, is withdrawn from drum 25 through line 26 and a first portion thereof is passed through line 17 as reflux for the extractor 14, with or without further heating, although without further heating is particularly shown. The remaining portion of the aromatic hydrocarbon phase in line 26 is passed through line 27 and introduced into the lower portion of a water wash column 28. A water wash is introduced into the upper portion of water wash column 28 through line 29 to countercurrently contact the aromatic hydrocarbon phase therein and as a result of such contact, the aromatic hydrocarbon phase is freed of remaining extraction solvent. The washed aromatic hydrocarbon phase is withdrawn from the top of column 28 through line 31 as product and the wash water, now containing extraction solvent, is withdrawn from the bottom of the column 28 through line 32 and treated to recover the extraction solvent, as hereinafter more fully described.

An extraction solvent phase, containing some aromatic hydrocarbon fraction, is withdrawn from settling drum 25 through line 33 and a first portion thereof passed through line 34 and heat exchangers 22 and 35 to effect heating thereof to the operating temperature of the extractor 14 by indirect heat transfer with the extract in line 19 and a suitable heat transfer agent, such as, steam, respectively. The heated extraction solvent from heat exchanger 35 is introduced into extractor 14 through line 16.

The remaining portion of the extraction solvent phase in line 33 is passed through line 36 to the upper portion of an extractor column 37, containing suitable liquidliquid contacting devices, such as, trays, and operated at a temperature no higher than 150 F., preferably at a temperature within the range between about 100 F. and about 120 F., and a pressure sufficient to maintain the components in the liquid phase. A non-aromatic hydrocarbon solvent, of the type hereinabove described such as, a C -C paraffin is introduced into the lower portion of the extractor 37 through line 38 to countercurrently contact the extraction solvent phase therein and as a result of such contact at the operating temperature of the extractor 37, the aromatic hydrocarbon fraction remaining in the extraction solvent is extracted therefrom into the nonaromatic hydrocarbon solvent.

An extraction solvent raflinate, essentially free of the aromatic hydrocarbon fraction, is withdrawn from extractor 37 through line 39, combined with extraction solvent recovered from wash water in line 41, as hereinafter described, and the combined stream in line 42 is recycled to the extractor 14, as hereinafter described.

An extract of the aromatic hydrocarbon fraction dissolved in the non-aromatic hydrocarbon solvent, is withdrawn from extractor 37 through line 51, passed through heat exchanger 52 to adjust the temperature thereof to the feed operating temperature of a fractionator 53 by indirect heat transfer with bottoms from the fractionator 53, an introduced into fractionator 53 to recover the aromatic hydrocarbon fraction. The fractionator 53 is operated at a temperature and pressure to separate the aromatic hydrocarbon fraction from the non-aromatic hydrocarbon and is provided with reboil, as generally indicated by 54, and reflux through line 55. As illustrated in FIG. 1, the non-aromatic hydrocarbon solvent has a boiling point lower than the aromatic hydrocarbon fraction and is recovered as overhead, but it is to be understood that a non-aromatic hydrocarbon solvent having a boiling point higher than the aromatic hydrocarbon fraction may also be employed in which case, the non-aromatic hydrocarbon solvent is recovered as bottoms.

A non-aromatic hydrocarbon solvent overhead is withdrawn from fractionator 53 through line 56, passed through condenser 57 to effect condensation thereof, and a portion of the condensed portion is introduced as reflux to the fractionator 53 through line 55. The remaining portion of non-aromatic hydrocarbon solvent in line 58 is passed through heat exchanger 59, supplied with a suitable coolant, such as water, to cool the non-aro matic hydrocarbon solvent to the operating temperature of the extractor 37 and introduced into extractor 37 through line 38.

An aromatic hydrocarbon bottoms is withdrawn from fractionator 53 through line 61, passed through heat exchangers 52 and 63 in an indirect heat transfer relationship with the feed to fractionator 53 and a suitable heat transfer agent, respectively combined with aromatic hydrocarbon product from wash column 28 in line 31 and the combined stream in line 62 passed to storage or additional processing.

The non-aromatic hydrocarbon rafiinate from extractor 14 in line 18 is sequentially passed through heat exchangers 43 and 71 to effect cooling thereof to a temperature below about 150 F., preferably a temperature within the range between about F. and about F. by indirect heat transfer with extraction solvent being recycled to the extractor 14, as hereinafter described and a suitable coolant such as water, respectively. The raffinate withdrawn from heat exchanger 71 is combined with all or a portion of the extraction solvent in line 42 and as a result of such combinations the extraction solvent dissolved in the rafiinate is transferred into the extraction solvent. The resulting mixture in line 72 is introduced into a settling drum 73 to separate the two phases. The extraction solvent phase is withdrawn from settler 73 through line 74 and sequentially passed through heat exchangers 43, 21 and 44 to effect heating thereof to the operating temperature of extractor 14 by indirect heat transfer with raflinate in line 18, extract in line 19 and a suitable heat transfer agent, such as steam, respectively. The heated extraction solvent is then introduced into extractor 14 through line 16. Alternatively, all or a portion of the extraction solvent in line 42 may be passed through line 70 directly to the heat exchanger 43, without prior combination with the raffinate, and in the case where all of the extraction solvent is passed directly to heat exchanger 43, the raffinate settler 73 is eliminated and the rafiinate is passed directly to the water wash, as hereinafter described.

A non-aromatic hydrocarbon phase, still containing some extraction solvent, is withdrawn from settler 73 through line 75 and introduced into the lower portion of a water wash column 76. A water wash is introduced into the upper portion of the column 76 through line 77 to countercurrently contact the non-aromatic hydrocarbon phase therein and as a result of such contact, the non-aromatic hydrocarbon phase is freed of remaining extraction solvent. The washed non-aromatic hydrocarbon phase is withdrawn from column 76 through' line 78 and passed to storage or further treatment.

Wash water, containing extraction solvent, is withdrawn from column 76 through line 79, combined with wash water containing extraction solvent in line 32 and the combined stream in line 81 passed through heat exchanger 82, wherein the temperature of the combined stream is adjusted to the operating feed temperature of a fractionator 83 by indirect heat transfer with bottoms from the fractionator 83. The combined stream from heat exchanger 82 in line 84 is introduced into the fractionator 83, operated at a temperature and pressure to separate the extraction solvent from the water, and provided with suitable recoil, as indicated at 85, and reflux through line 86.

An extraction solvent overhead is withdrawn from fractionator 83 through line 87, passed through condenser 88 to effect condensation thereof and a portion introduced as reflux to the fractionator 83 through line 86. The remaining portion of extraction solvent in line 41 is combined with extraction solvent in line 42 for recycle to the extractor 14, as hereinabove described.

A water bottoms is withdrawn from fractionator 83 through line 91, passed through heat exchanger 82 and heat exchanger 92, provided with a suitable coolant, such as water, and a portion thereof passed through line 93 to waste after treatment to recover a substantial portion of any dissolved Group I or Group II metal salt modifier. The remaining portion of the water in line 94 is combined with make-up water in line 95 and passed to water wash columns 28 and 76 through lines 29 and 77, respectively.

The process of the invention as hereinabove described with respect to FIG. 1 may be modified in numerous ways within the spirit and scope thereof. Thus, for example, the various heat transfer steps may be effected otherwise than as particularly described; e.g., the bottoms recovered from fractionator 53 could be passed to further processing without cooling. As a further modification, if the aromatic hydrocarbons recovered in fractionator 53 still contains some extraction solvent, the aromatic hydrocarbon bottoms may be combined with the aromatic hydrocarbon stream in line 27 to effect water washing thereof.

As another modification, if the extraction solvent would form undesirable azotropes in the fractionator 53, then the extract from extractor 37 in line 51 would be water washed to eflfect removal of extraction solvent prior to introduction thereof into fractionator 53.

A still further modification of the embodiment of the invention described with reference to FIG. 1 is illustrated in FIG. 2 wherein like parts are designated by like prime numerals, with the embodiment of FIG. 2 differing from the embodiment of FIG. 1 in that non-aromatic hydrocarbon solvent of the type employed in extractor 37 is also employed in extractor 14. In addition, the water washing of various streams, including wash columns and wash fractionator, of the embodiment of FIG. 2 are schematically indicated as a wash Zone 102 to facilitate the description thereof.

Referring now to FIG. 2, a non-aromatic hydrocarbon solvent of the type hereinabove described, in line 101 is combined with aromatic hydrocarbon reflux in line 17' and introduced into the extractor 14'. It is to be under stood, that the non-aromatic hydrocarbon solvent could either be introduced into the lower portion (extract portion) of the extractor 14' with no extract reflux, or preferably in combination with extract reflux, as shown. As a result of the introduction of the non-aromatic hydrocarbon solvent into the extractor 14, both the raflinate in line 18' and the extract in line 19' contain non-aromatic hydrocarbon solvent, and additional processing steps are required to eflect recovery thereof.

The aromatic hydrocarbon phase from settler in line '27 contains a relative small portion of non-aromatic hydrocarbon solvent. In accordance with the embodiment of FIG. 2, the aromatic hydrocarbon phase is passed through heat exchanger 104, located upstream of heat exchanger 52, in an indirect heat transfer relationship with aromatic bottoms from fractionator 53' and introduced into fractionator 53 through line 105, positioned below line 51' for introducing the extract from embodiment of FIG. 1, fractionator 53 operates to separate the aromatic hydrocarbon fraction from the non-aromatic hydrocarbon solvent with the aromatic hydrocarbon fraction being recovered as bottoms. The aromatic bottoms is cooled by indirect heat transfer in heat exchanges 104-, 52' and 63 and then water washed in water wash zone 102.

A non-aromatic hydrocarbon solvent overhead is withdrawn from fractionator 53 through line 106, combined with non-aromatic hydrocarbon solvent recovered from the raifinate from extractor 14 in line 107, as hereinafter described, condensed in condenser 108 and divided into three portions. One portion is employed as reflux for fractionator 53, a second portion is passed through line 109 as refiux for a fractionator for recovering non-aromatic hydrocarbon solvent from the raffinate from extractor 14, as hereinafter described, and a third portion, after cooling in heat exchanger 111 is passed through line 101 for introduction into the extractor 14'.

The non-aromatic hydrocarbon phase recovered as rafiinate from extractor 14, contains a major portion of the non-aromatic hydrocarbon solvent introduced through line 17. In accordance with the embodiment of FIG. 2, the non-aromatic hydrocarbon in line 75 is passed through heat exchanger 122 in an indirect heat transfer relationship with bottoms from fractionator 123 and introduced into the fractionator 123. The fractionator 123 is operated at a temperature and pressure to separate the non-aromatic hydrocarbon from the non-aromatic hydrocarbon solvent and is provided with reboil as indicated at 123 and reflux through line 109. A non-aromatic hydrocarbon fraction bottoms is withdrawn from fractionator 123 through line 125, passed through heat exchangers 122 and 126, washed in water wash zone 102 and passed to storage or further treatment. A non-aromatic hydrocarbon solvent overhead is withdrawn from fractionator 123 through line 107 and combined with the overhead in line 106, as hereinabove described.

In accordance with the embodiment of FIG. 2, the incorporation of a non-aromatic hydrocarbon solvent in extractor 14 results in a reduced circulation of extraction solvent and a reduction in the number of contacting stages in extractor 14'. Similarly to the embodiment of FIG. 1, the embodiment of FIG. 2, may be modified in numerous ways within the spirit and scope of the inven tion. Thus, for example, instead of washing the aromatic hydrocarbon and non-aromatic hydrocarbon fractions after recovery in fractionators 53' and 123, the feeds to these fractionators may be Water washed, if the relatively small quantities of extraction solvent present in these streams should form undesirable azeotropes when distilled.

The preferred non-aromatic hydrocarbon solvents for the embodiment of FIG. 2 are paraflins with a boiling point or range lower than the boiling range of the feedstock mixture. However, as another modification, the non-aromatic hydrocarbon solvent employed may have a boiling point or range below the boiling point or range of all components of the liquid hydrocarbon feed in line 10, in which case, the non-aromatic hydrocarbon solvent is recovered as bottoms in fractionators 53 and 123.

As still another modification the various heat transfer steps may be effected in a manner otherwise than as particularly described.

A further modification of the embodiment of the in vention described with reference to FIG. 2 is illustrated in FIG. 3 wherein like parts are designated by like double prime numerals, with the embodiment of FIG. 3 differing from extractor 14' and treated to recover non-aromatic hydrocarbon solvent.

Referring now to FIG. 3, a stream, containing the arematic hydrocarbon and non-ar0matic hydrocarbon fractions introduced into extractor 14" through line 13 and the non-aromatic hydrocarbon solvent introduced into the extractor 14" through lines 101" and 17 is withdrawn from the lower portion of extractor 14", preferably at the stage immediately below the feed inlet (line 13"), through line 201 and introduced into a fractionator 203. The fractionator 203 is operated at a temperature and pressure to separate the non-aromatic hydrocarbon solvent from the non-aromatic hydrocarbon and aromatic hydrocarbon fractions and is provided with reboil as in dicated at 204 and reflux through line .205. A non-aromatic hydrocarbon solvent overhead is withdrawn from fractionator 203 through line 206, combined with the overhead from fractionator 123" in line 107" and treated as hereinabove described with reference to FIG. 2. A hottoms, containing the non-aromatic hydrocarbon and aromatic hydrocarbon fractions, is Withdrawn from fractionator 203 through line 207 and introduced into the extractor 14" at a point in proximity to the point from which the stream was withdrawn from the extractor 14"; as shown in the drawing the stream in line 207 is combined with the feed in line 13".

In accordance with the embodiment of FIG. 3, the rovision of an intermediate draw-off stream from the extractor 14" reduces the flow in the rafiinate stripping section of extractor 14 by essentially maintaining the non-aromatic hydrocarbon solvent in the extract portion of the extraction thereby further reducing the total circulation of extraction solvent.

The embodiment of FIG, 3 may also be modified in numerous ways within the spirit and scope of the invention; e.g., as described with reference to the embodiment of FIG. 2, and such modifications are deemed to be within the scope of one skilled in the art. In addition, it is to be understood that the extraction may be effected in more than one extractor and therefore the stream may be withdrawn from the overall extraction from a point other than as shown.

Still another embodiment of the process of the invention is illustrated in FIG. 4. Referring now to FIG. 4, a feed containing aromatic and non-aromatic hydrocarbon fractions, in line 400 is passed through an absorbent drier 401 and through heat exchangers 411 and 412 to effect heating thereof to a temperature suitable for extraction of the aromatic hydrocarbon fraction therefrom by indirect heat transfer with extract from an extraction column, as hereinafter more fully described, and a suitable heat transfer agent; e.g., steam, respectively. The heated mixture from heat exchanger 412 in line 413 is introduced into the lower portion of an extraction column 414, containing a plurality of suitable liquid-liquid contacting devices, such as trays, and operated at a temperature within the range between about 200 F. and about 400 F. and a pressure suflficient to maintain components in the liquid phase. A lean extraction solvent of the type hereinabove described, is introduced into the top of extractor 414 through line 415 and additional extraction solvent is introduced through line 416 at an intermediate portion of the extractor 414. The extractor 414 is provided with an aromatic hydrocarbon reflux through line 417 located at the bottom of the extractor 414. As a result of the contact between the mixture and the extraction solvent, the aromatic hydrocarbon fraction is extracted from the mixture with a non-aromatic hydrocarbon rafiinate, essentially free of aromatic hydrocarbons, being withdrawn from the top of the extractor 414 through line 418 and an extract composedof a solution of the aromatic hydrocarbon fraction in the extraction solvent, essentially free of non-aromatic hydrocarbons, is withdrawn from the bottom of the extractor 414 through line 419.

The extract in line 419 is passed through heat exchangers 420, 411, 422, 423 and 424 to effect cooling thereof to a temperature below 150 F., preferably to a temperature within the range between about 100 F. and about 120 F. by indirect heat transfer with extraction solvent being recycled to the extractor 414 through line 415,, feed in line 400, aromatic product, extraction solvent being re- 10 cycled to the extractor 414 through line 416, and a suitable coolant, such as water respectively. As a result of such cooling, a major portion of the aromatic hydrocarbon fraction is now insoluble in the extraction solvent and a two phase mixture is introduced into a settling drum 425 to separate the two phases.

An aromatic hydrocarbon phase, containing some extraction solvent, is withdrawn from drum 425 through line 426 passed through heat exchanger 422, and a first portion thereof is passed through line 417 as reflux for the extractor 414, after heating in an exchanger 430. The remaining portion of the aromatic hydrocarbon phase in line 426 is passed through line 427 and introduced into the lower portion of a fractionator 453 to recover any remaining non-aromatic hydrocarbons therefrom as hereinafter described.

An extraction solvent phase, containing some aromatic hydrocarbon fraction, is withdrawn from settling drum 425 through line 433 and a first portion thereof passed through line 434 and heat exchangers 423 and 435 to effect heating thereof to the operating temperature of the extractor 414 by indirect heat transfer with the extract in line 419 and a suitable heat transfer agent, such as, steam, respectively. The heated extraction solvent from heat exchanger 435 is introduced itno extractor 414 through line 416.

The remaining portion of the extraction solvent phase in line 433 is passed through line 436 to the upper portion of an extraction column 437, containing suitable liquid-liquid contacting devices, such as trays, and operated at a temperature no higher than 150 F., preferably at a temperature within the range between about F. and about F., and a pressure suflicient to maintain the components in the liquid phase. A non-aromatic hydrocarbon solvent, of the type hereinabove described such as, a C -C paraflin is introduced into the lower portion of extractor 437 through line 438 to countercurrently contact the extraction solvent phase therein and as a result of such contact at the operating temperature of the extractor 437, the aromatic hydrocarbon fraction remaining in the extraction solvent is extracted therefrom into the non-aromatic hydrocarbon solvent.

An extraction solvent raffinate, essentially free of any aromatic hydrocarbon fraction, is withdrawn from extractor 437 through 439, and combined with rafiinate from extractor 414 as hereinafter described.

An extract of the aromatic hydrocarbon fraction dissolved in the on-aromatic hydrocarbon solvent, is withdrawn from extractor 437 through line 451, passed through heat exchanger 452 to adjust the temperature thereof to the feed operating temperature of a fractionator 453 by indirect heat transfer with raffinate from extractor 414 and introduced into fractionator 453 to recover the aromatic hydrocarbon fraction. The fractionator 453 is operated at a temperature and pressure to separate the aromatic hydrocarbon fraction from the nonaromatic hydrocarbon solvent and is provided with reboil, as generally indicated by 454, and reflux through line 455.

A non-aromatic hydrocarbon solvent overhead is withdrawn from fractionator 453 through line 456, passed through condenser 457 to effect condensation thereof, and a portion of the condensed portion is introduced as reflux to the fractionator 453 through line 455. The remaining portion of non-aromatic hydrocarbon solvent in line 458 is passed through heat exchanger 459, supplied with a suitable coolant, such as water, to cool the non-aromatic hydrocarbon solvent to the operating temperature of the extractor 437 and introduced into extractor 37 through line 438.

An aromatic hydrocarbon bottoms is withdrawn from fractionator 453 through line 461, and passed while hot to a recovery zone (not shown) to recover the various aromatic components.

The non-aromatic hydrocarbon raffinate from extractor 414 in line 418 is sequentially passed through heat exchangers 452 and 471 to effect cooling thereof to a temperature below about 150 F., preferably a temperature within the range between about 100 F. and about 120 F. by indirect heat transfer with extract from extractor 437 in line 451 and a suitable coolant, such as water, respectively. The reafiinate withdrawn from heat exchanger 471 is combined with the extraction solvent in line 439 and as a result of such combination the extraction solvent in the rafiinate from extractor 414 is transferred into the extraction solvent, and sequentially passed through heat exchangers 420 and 470 to effect heating thereof to the operating temperature of extractor 414.

A non-aromatic hydrocarbon phase, still containing some extraction solvent, is withdrawn from settler 473 through line 475 and introduced into the lower portion of a water wash column 476. A water wash is introduced into the upper portion of the column 476 through line 477 to countercurrently contact the non-aromatic hydrocarbon phase therein and as a result of such contact, the non-aromatic hydrocarbon phase is freed of remaining extraction solvent. The washed non-aromatic hydrocarbon phase is withdrawn from column 476 through line 478 and passed to storage or further treatment.

Wash water, containing extraction solvent, is withdrawn from column 476 through line 479, passed through heat exchanger 482, wherein the temperature of the combined stream is adjusted to the operating feed temperature of a fractionator 483 by indirect heat transfer with bottoms from the fractionator 483, and introduced into the fractionator 483, operated at a temperature and pressure to separate the extraction solvent from the water, and provided with suitable reboil, as indicated at 485, and reflux through line 486.

An extraction solvent overhead is wtihdrawn from fractionator 483 through line 487, passed through condenser 488 to effect condensation thereof and a portoin introduced as reflux to the fractionator 483 through line 486. The remaining portion of extraction solvent in line 487 is combined with feed in line 400 for passage through drier 401.

A water bottoms is Withdrawn from fractionator 483 through line 491, passed through heat exchanger 482 and heat exchanger 492, provided with a suitable coolant, such as water, and introduced into wash column 476 through line 477.

The embodiment of FIG. 4 may also be modified in numerous ways within the spent and scope of the invention; e.g., as described with reference to FIGS. 1, 2 and 3, and such modifications are deemed to be Within the scope of one skilled in the art.

The invention is further described with respect to the following example which illustrates operating conditions which may be employed in practising the invention but the scope of the invention is not to be limited thereby.

EXAMPLE The conditions of Table II are employed to extract the aromatic hydrocarbon fraction from the feedstock mixture of Table I with an extraction solvent of methanol containing 20 weight percent of lithium chloride. The nonaromatic hydrocarbon solvent employed in extractor 37 is pentane. The processing scheme is essentially as shown in FIG. 1.

TABLE II Temperature, Pressure, Flow rate, F p.s.i.g. lbs/hr.

The aromatic hydrocarbon fraction recovered through lines 31 and 61 has the following composition:

The recovery of aromatic constituents in the aromatic hydrocartmn fraction is approximately:

Component: Weight percent Benzene 99.9 Toluene 99 C aromatics 96 C aromatics 85 The non-aromatic hydrocarbon fraction recovered in line 78 has the properties:

ASTMBoiling range, 210-320 F. APIGravity, 59 API The process of the invention is extremely effective for separating and recovering aromatic and non-aromatic hydrocarbon fractions from mixtures thereof. The use of the highly polar organic liquid, containing a metal salt modifier, as the initial extraction solvent permits selective dissolution of aromatic hydrocarbons therein at an elevated temperature and separation of aromatic hydrocarbons at a lower temperature. In addition, at lower temperatures, aromatic hydrocarbons contained in the extraction solvent may be extracted therefrom with a non aromatic hydrocarbon solvent, permitting essentially complete recovery of the aromatic hydrocarbon fraction and recycle of lean extraction solvent. Accordingly, the process of the invention may be economically operated on a continuous commercial basis. Thus, for example, the process of the invention may be employed to recover benzene, toluene, xylenes and other aromatics from naphtha fractions, including catalytically reformed naphtha, or hydrotreated naphtha from pyrolysis operations. The raflinate separate from the said naphtha is suitable as a low-octane gasoline blending stock, for recycling to catalytic reforming or pyrolysis operations, or for blending to military jet fuel, JP-4. The aromatic extract separated from the said naphtha may either be further processed to aromatic petrochemicals or utilized as a high-octane gasoline blending stock.

In addition, the process of the invention may be readily adapted to upgrade kerosene, jet fuel, diesel fuel, lube oils, and recycle oils from catalytic cracking operations known as cat cycle oils, by extracting a major portion of the aromatic constituents which are undesirable in these stocks. The aromatic extracts separated from the said gas oils and lube oils represent valuable byproducts which can be used in the manufacture of carbon black, asphalt, sulfonates, naphthalene and other petrochemicals, fuel oil, coke, etc.

In applications involving benzene, toluene and xylene (BTX) separation from naphtha fractions, the economics of this process appear somewhat more favorable than for the presently practiced BTX extraction processes. The solvent system offers the unique properties of excellent capacity and high selectivity for BTX at high temperatures, with reduced capacity for BTX at low temperatures. These properties permit the recovery of a large portion of the aromatic constituents from the rich solvent by simple cooling followed by decantation. The equipment costs and utilities consumption are somewhat reduced by this approach, in comparison to the present commercial BTX processes, which employ distillation to separate the entire aromatic fraction from the solvent. In the process of the invention distillation is employed to recover only that portion of the aromatics fraction which is unobtainable by cooling and decantation. Since distillation costs represent a major portion of the overall processing cost for all BTX extraction processes, significant savings are possible using the process of the invention.

Numerous modifications and variations of the present invention are possible in light of the above teachings and therefore the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A process for separating an aromatic hydrocarbon fraction and a non-aromatic hydrocarbon fraction from a liquid mixture thereof, comprising:

(a) contacting the mixture at an elevated temperature with an extraction solvent selective for aromatics having a soluble salt modifier selected from the group consisting of salts of copper, silver, beryllium, magnesium, zinc, tin, vanadium, arsenic, antimony, bismuth, chromium, magnanese, iron, cobalt, nickel, palladium and platinum dissolved therein, whereby the aromatic hydrocarbon fraction is extracted from the mixture;

(b) separating a non-aromatic hydrocarbon fraction from the extraction solvent containing the aromatic hydrocarbon fraction;

(0) cooling the extraction solvent, containing the aromatic hydrocarbon fraction to a temperature at least about 100 F. lower than the temperature of extraction of step (a), whereby a substantial portion of the aromatic hydrocarbon fraction is rendered insoluble in the extraction solvent; and

(d) separating the insoluble aromatic hydrocarbon fraction from the extraction solvent.

2. The process as defined in claim 1 wherein the salt modifier is selected from the group consisting of soluble salts of lithium, beryllium and magnesium.

3. The process as defined in claim 2 wherein the extraction of step (a) is effected at a temperature from about 200 F. to about 400 F. and cooling in step (c) is effected to a temperature no greater than about 150 F.

4. The process as defined in claim 3 wherein the extraction solvent is methanol, containing between about and about 50 weight percent of lithium chloride.

5. The process as defined in claim 3 and further comprising: (e) contacting at least a portion of the extraction solvent from step (d) with a non-aromatic hydrocarbon solvent having a boiling point which is different from the boiling point of the aromatic hydrocarbon fraction to extract the remaining aromatic hydrocarbon fraction from the extraction solvent, said contacting being effected at a temperature no greater than about F.; (f) recycling the extraction solvent to step (a); and (g) fractionating the non-aromatic hydrocarbon solvent containing the extracted aromatic hydrocarbon fraction to recover the aromatic hydrocarbon fraction therefrom.

'6. The process as defined in claim 5 wherein a portion of the extraction solvent from step (d) is contacted with the non-aromatic hydrocarbon solvent as defined in claim 5 and the remaining portion is recycled to step (a).

7. The process as defined in claim 6 wherein a portio of the aromatic hydrocarbon fraction recovered in step (d) is passed to the fractionation of step (g) of claim 5.

8. The process as defined in claim 5 ad further comprising: employing a non-aromatic hydrocarbon solvent in step (a) having a boiling point or range different from the boiling range of the aromatic and non-aromatic hydrocarbon fraction of the mixture, fractionating the nonaromatic hydrocarbon fraction recovered in step (b) to separate the non-aromatic hydrocarbon from the nonaromatic hydrocarbon solvent, recycling the separate non-arornatic hydrocarbon solvent to step (a), fractionating at least a portion of the aromatic hydrocarbon fraction separated in step (d) to separate non-aromatic hydrocarbon solvent therefrom and recycling the non-aromatic hydrocarbon solvent separated from the aromatic hydrocarbon fraction to step (a).

9. The process as defined in claim 6 wherein step (a) is effected in a plurality of extraction stages and further comprising: withdrawing from step (a) a stream from an intermediate stage containing the aromatic hydrocarbon and the non-aromatic hydrocarbon fraction of the mixture and the non-aromatic hydrocarbon solvent, fractionatiug the withdrawn stream to separate the non-aromatic hydrocarbon solvent therefrom, and recycling the remaining portion of the withdrawn stream to an extraction stage in proximity to the extraction stage from which the stream was withdrawn.

10. A process for separating an aromatic hydrocarbon and a non-aromatic hydrocarbon fraction from a liquid mixture thereof, comprising:

(a) introducing the liquid mixture into a liquid-liquid extraction zone operated at a temperature within the range between about 200 F; and about 400 F.

(b) introducing an extraction solvent selective for aromatics having a soluble salt modifier selected from the group consisting of salts of lithium, beryllium and magnesium, dissolved therein into the extraction zone to contact said liquid mixture whereby the extraction solvent selectively extracts the aromatic hydrocarbon fraction from the mixture;

(c) withdrawing a raffinate from the extraction zone comprised of the non-aromatic hydrocarbon fraction essentially free of aromatic hydrocarbons;

(d) withdrawing an extract from the extraction zone comprised of the aromatic hydrocarbon fraction dissolved in the extraction solvent;

(e) cooling the extract to a temperature no higher than about 150 F., whereby a substantial portion of the aromatic hydrocarbon fraction is rendered insoluble in the extraction solvent;

(f) separating and recovering the insoluble portion of the aromatic hydrocarbon fraction from the extraction solvent;

(g) recycling a portion of the extraction solvent from step (f) to step (b);

(h) introducing another portion of the extraction solvent from step (f) into another extraction zone operated at a temperature no higher than about 150 F;

(i) introducing a non-aromatic hydrocarbon solvent,

having a boiling point or range different than the aromatic hydrocarbon fraction into the another extraction zone to contact said extraction solvent, whereby 15 the non-aromatic hydrocarbon solvent selectively extracts the aromatic hydrocarbon fraction from the extraction solvent;

(j) withdrawing a raffinate of the extraction solvent essentially free of any aromatic hydrocarbon fraction from the another extraction zone and recycling the rafiinate from the another extraction zone to D (k) withdrawing an extract from the another extraction zone comprised of a aromatic hydrocarbon fraction dissolved in the non-aromatic hydrocarbon solvent;

(1) fractionating the extract from step (k) to separately recover the non-aromatic hydrocarbon solvent and the aromatic hydrocarbon fraction; and

(in) recycling the non-aromatic hydrocarbon solvent to step (i).

11. The process as defined in claim 10 and further comprising passing a portion of the aromatic hydrocarbon fraction recovered in step (t) to the fractionating of step (1).

12. The process as defined in claim 10 wherein the extraction solvent is methanol containing between about 10 and about 50 weight percent of lithium chloride.

13. The process as defined in claim 12 wherein the boiling point or range of the non-aromatic hydrocarbon solvent is different from the boiling range of all components of the liquid mixture and further comprising: introducing the non-aromatic hydrocarbon solvent into the extract enriching portion of the extraction zone contain'the nonaromatic hydrocarbon solvent; fractionating the rafiinate from the extraction zone to separate the non-aromatic hydrocarbon solvent therefrom; fractionating at least a portion of the aromatic hydrocarbon fraction recovered in step (f) to separate the non-aromatic hydrocarbon solvent therefrom and recycling non-aromatic hydrocarbon solvent recovered from the raffinate and the aromatic hydrocarbon fraction to the extraction zone.

14. The process as defined in claim 12 wherein the extraction zone contains a plurality of extraction stages and further comprising: withdrawing a stream from an intermediate stage of the extraction zone, the stream containing the aromatic and non-aromatic hydrocarbon fractions of the mixture and the non-aromatic hydrocarbon solvent; fractionating said stream to separate the non-aromatic hydrocarbon solvent therefrom; recycling non-aromatic hydrocarbon solvent separated from the stream to the extract portion of the extraction zone and recycling the remaining portion of the stream to a stage in the extraction zone in proximity to the stage from which the stream was withdrawn.

References Cited UNITED STATES PATENTS 2,133,691 9/1938 Francis 2()8324 2,142,939 1/1939 Francis 208-324 2,154,372 4/1939 Bosing 208324 2,246,257 6/1941 Kohn 208324 HERBERT LEVINE, Primary Examiner US. Cl. X.R.

1 Maw, U" r Te U chliiigrlcmim O: COPml-JCTLON Patent No. 3 5 0 335 Dd'ccd F b uary 2 1971 I h) GELBIEN ET AL It'ia certified that error appears in the above-identified potent and that said Letters Patent are hereby corrected as shown below;

Column 2, line 30, after lower insert "hydrocarbon (preferably acyclic) and substituted ''"and delete "acyclic and heterocyclic hydrocarbon amines and".

Column 2, line 33, "heterochclic." should be --heterocyc li-c.

Column 7, line '75, after "from" insert extract0r 37 As .hereinabove described with respect. to the Column 8, line'5, "exchn ges" should be '--exchangers. Column l0, li ne 25, "itno" should be --into. Column 10, 1ine 48, "onsrornalzie should be "non-aromatic. Columrrll, line 6, "reaffirlate" should be raffinate--.

Column-"11', fline 34, 'wtihdrawn" should be -withdrawn Columnfill, line 36, "portoin" should be -portion.

Column? 12,.1ine 69, "separate" should be -separated-.

Columrrll, lines 12 and 13,- "por-tio" should be -portion.

L. y Columnl, li ne 16,-"ad" should be -and--.

Signed ahd sealed this 10th day of Au usfp 1971.

(SEAL) Ir Attest: t 1 1 T CHER WILLIAM E. SCHUYIER, JR. EDWARD M FLE )J'R Commiossioner of Patents Attesting Officer 

